Print either:

1) Mini marshmallow gun(printable)
or
2) Mini marshmallow left (printable)
Mini marshmallow Right (printable)
Mini marshmallow mouthpiece(printable)

Acquire:
4 X M3 20mm socket head screws
4 X M3 Locking nuts
1 X 500-250mm 1/2" CPVC Plastic pipe. (This can be found at any hardware store in the plumbing section. CPVC has a small inside diameter than 1/2 PVC better suited for mini marshmallow)

Assembly:

Bolt Left and right side together towards the front of the plastic.
Add mouthpiece to the back.

Loading techniques:

Refer to picture entitled "How to Load marshmallow Rifle"

Ammo:

Mini marshmallows

Specs:

Mini Marshmallow gun: 250mm long barrel
Range:45 feet

Mini Marshmallow rifle: 500mm long barrel
Range:60 feet

Infill:
Mini marshmallow handle:
3 outside perimeters
3 layer solid
15% infill
0.25mm layer height

Mini marshmallow mouthpiece:
3 outside perimeters
3 layer solid 
25% infill
0.25mm layer height

Warning: This Item is a toy, but adult supervision is required. Do not run with the Mini marshmallow gun in your mouth. Always were proper safety glass while operating this item.